In recent years, there has been a growing interest in power generation using renewable energy such as solar light and wind power from the viewpoint of global environmental protection. However, since such renewable energy decreases stability due to its dependence on weather conditions or the like, it appears to be difficult for the renewable energy to play a role as a base power source.
Conversely, solar power using solar heat generates power in such a manner that it concentrates solar light with a lens and rotates a turbine with steam generated by heat resulting from the concentration of the solar light. That is, provided that solar light strongly beats down at all times, it is possible to generate power stably and inexpensively. For this reason, countries having desert regions and dry regions have promoted the introduction of the solar power generation, and there has been a growing demand for solar thermal energy excellent in cost-effectiveness and reliability on an international basis.
The storage of solar thermal energy is a recommended technology for responding to the demand for solar thermal energy excellent in cost-effectiveness and reliability since the thermal energy concentrated in a concentrated solar power (CSP) system can be directly stored without the need to transform the solar thermal energy to another energy form. Note that the thermal energy can be stored in an insulated container and collected through a heat engine or the like that generates electricity (i.e., it can be transformed to electric energy).
As for solar power, Patent Literature 1, e.g., proposes a solar light heat collector that collects solar thermal energy with high efficiency and high quality and stores the same in a heating medium, a solar light concentrating reflector, a solar light concentrating system, and a solar light energy using system, each using the solar light heat collector.
In addition, Patent Literature 1 discloses a beam-down solar light concentrating system as a system that concentrates solar light. Note that the beam-down solar light concentrating system is also disclosed in Non-Patent Literature 1.
Here, as shown in FIG. 6, the beam-down solar light concentrating system refers to a system in which a plurality of reflecting mirrors (heliostats) 61 is arranged on the ground and the reflection light of solar light SB reflected by the plurality of heliostats 61 is reflected downward by a light concentrating reflecting mirror 62 provided at a high place and concentrated into a heat collector 63.